Known thread seals as disclosed for example in the U.S. Pat. Nos. 2,706,656; 2,982,573; and 3,009,722 are suited only for static seal applications because the elastomeric rings thereof are in high pressure frictional engagement with the threads of a bolt or screw. In the U.S. Pat. No. 3,259,404 the thread seal is provided with three equally spaced projections shaped to engage the flanks and root of the thread whereby the bore of the ring need only be embedded partway into the crest of the thread. However, even if one projection registers with the thread groove, the other two projections will be subject to high pressure axial shearing forces by the flanks of the thread.